1. Field of the Invention
The present application relates to a structure of isolation of a photoelectric conversion apparatus.
2. Description of the Related Art
CCD type and CMOS type photoelectric conversion apparatuses are used for a lot of digital still cameras and digital camcorders. In recent years, in the photoelectric conversion apparatuses, pixels have been reduced. Thus, measures against charge leakage (cross talk) into adjacent pixels that occurs according thereto are discussed.
Japanese Patent Application Laid-Open No. 2003-258232 discloses a configuration where a P type well region, which functions as a barrier for element isolation to prevent charge leakage (cross talk) between adjacent pixels, is formed in a deep region consistent with an N type well region of a photoelectric conversion element.
However, even with the P type well region disclosed in Japanese Patent Application Laid-Open No. 2003-258232, it may be difficult to sufficiently suppress charge leakage.
In general, in the photoelectric conversion apparatus, a transistor for reading charge from a photoelectric conversion element is provided around the photoelectric conversion element. Here, there is a case where the widths of semiconductor regions functioning as element isolation regions for separating the photoelectric conversion elements from each other vary. The inventors of the present invention have found that there is a case where amounts of leakage of charge from P type well regions, which can be element isolation of the photoelectric conversion elements described in Japanese Patent Application Laid-Open No. 2003-258232, may vary according to the widths of the element isolation regions in such situations. If amounts of leakage of signal charge into the adjacent photoelectric conversion elements vary, the image quality is degraded and correction of the image signal becomes difficult.
Thus, it is an object of the present invention to provide a photoelectric conversion apparatus capable of reducing variation in charge leaking into the adjacent photoelectric conversion elements (pixels).